With respect to a metal oxide sol containing a hydrophobic organic solvent as the dispersion medium, for example, known is a production method of an organic solvent dispersed inorganic oxide sol in which inorganic oxide fine particles in which a C3-12 primary alkoxy group is bonded to a silicon atom on the surface of the inorganic oxide fine particle, are stably dispersed in an organic solvent such as methyl ethyl ketone (see Patent Document 1).
Furthermore, disclosed are a stable sol containing: a structure in which a colloidal particle of stannic oxide and a colloidal particle of zirconium oxide are bonded with each other in a ZrO2/SnO2 ratio based on the weight of these oxides of 0.02 to 1.0; and a modified stannic oxide-zirconium oxide complex colloidal particle having a particle diameter of 4.5 to 60 nm which is formed by coating the surface of a stannic oxide-zirconium oxide complex colloidal particle having a particle diameter of 4 to 50 nm as the core with a tungsten oxide-stannic oxide-silicon dioxide complex colloidal particle having a WO3/SnO2 mass ratio of 0.1 to 100, an SiO2/SnO2 mass ratio of 0.1 to 100, and a particle diameter of 2 to 7 nm, and containing 2 to 50% by mass of all the metal oxides, and a production method for the same (see Patent Document 2).